Thermoplastic composition comprising vinyl chloride polymer and diolefinmono-vinylpyridine copolymer



United States Patent "ice THERMOPLASTIC COMPOSITION COMPRISING VINYLCHLORIDE POLYMER AND DIOLEFIN- MONO-VINYLPYRIDINE COPOLYMER Pliny O.Tawney, Passaic, and Roger W. Amidon, Oakland, N. .l'., assignors toUnited States Rubber Company, New York, N. Y., a corporation of NewJersey No Drawing. Application May 4, 1953, Serial No. 353,010

8 Claims. (Cl. 260-45.5)

This invention relates to improved thermoplastic compositions which arerigid and yet have a high impact strength, and more particularly itrelates to thermoplastic compositions comprising blends of unplasticizedvinyl chloride polymers with relatively small amounts of a copolymer ofa conjugated diolefin and a vinylpyridine.

The ordinary polyvinyl chloride of commerce is a hard, rigid, chemicallyresistant thermoplastic polymer which has come into widespread use in alarge variety of applications because of its desirable combination ofphysical properties. However, the material has one major disadvantage,namely, relatively poor impact resistance, which precludes itssuccessful use in fabricating rigid articles that must withstand blowsin normal usage. When polyvinyl chloride is compounded with relativelylarge amounts of soluble plasticizers (e. g., 50-100 parts ofplasticizer per 100 parts of polyvinyl chloride) the resulting productsare flexible, soft materials suitable for forming films and the like,but the mixing of hard, rigid articles therefrom is entirely precluded.

One object of the present invention is tocompound polyvinyl chloride insuch a way as to retain its rigidity, hardness and flexural strength andto raise its impact strength significantly.

Another object of the invention is to produce improved polyvinylchloride compositions capable of being fabricated into non-brittle,tough, rigid articles, which substantially retain the excellent chemicalresistance and resistance to heat distortion that are characteristic ofthe polyvinyl chloride itself.

According to the invention, a major amount of an unplasticized vinylchloride polymer is compounded with a minor amount of a rubberycopolymer of a conjugated diolefin with a mono-vinylpyridine, and themixture is fusion-blended. This combination of materials has mostunexpectedly been found to result in a spectacular improvement in theimpact strength. Furthermore, in these mixtures the unexpectedimprovement in impact strength is obtainable without reducing therigidity significantly. The invention therefore provides improved vinylchloride polymer compositions which are rigid but non-brittle, and aretherefore adapted to formation of rigid sheets or films, or otherarticles capable of rendering excellent service, even in applicationswhere polyvinyl chloride has heretofore been considered totallyunsuited.

The vinyl chloride polymer used in the invention may be either polyvinylchloride itself, or a copolymer of vinyl chloride with anothercopolymerizable monomer, the latter usually being a monoethylenicallyunsaturated material, such as vinyl acetate or vinylidene chloride.These polymeric materials will be designated generally as vinyl chloridepolymers.

The elastomeric copolymer component of the mixture of this invention isdefined as a copolymer of a conjugated diolefin with a vinylpyridine.

The conjugated diolefin is usually butadiene, but it can 2,780,615Patented Feb. 5, 1957 be one of the homologs thereof, of which isopreneand piperylene are the most important.

Any mono-vinylpyridine can be copolymerized with the diolefin to formthe elastomer. The pyridine ring can be otherwise unsubstituted or itcan be substituted elsewhere with an allcyl group. Examples of suitablemonovinylpyridines are: 2-vinylpyridine, Z a-vinylpyridine,4-vinylpyridine, Z-methyl 5 vinylpyridine, 5 ethyl-2-vinylpyridine, 2methyl 6 vinylpyridine and 2 ethyl 4- vinylpyridine. It will be notedthat all of the foregoing compounds are monoethylenically unsaturated.

The relative proportions of combined monomers in the elastomericcopolymers can vary widely; e. g., usually from about 40 to of adiolefin is copolymerized correspondingly with from about 60 to 20% of amonovinylpyridine.

The compositions of the invention contain, in parts of the blend, fromabout 2 parts to about 20 parts by weight of the vinylpyridinecopolymer, and conversely from about 98 parts to about 80 parts of thevinyl chloride polymer. Compositions containing less than about 2 partsof the rubbery copolymer do not show a satisfactory improvement inimpact strength. On the other hand, it is found that compositionscontaining more than about 20 parts of the rubbery copolymer have verylow tensile strength, low rigidity, and low tear resistance, as Well asa very poor physical appearance characterized by excessive lumpiness,and are of no value in making rigid articles of high impact strength.The preferred compositions contain from about 3 parts to about 15 partsof the'vinylpyridine copolymer in 100 parts of the blend of copolymerand vinyl chloride polymer.

However, these broader composition limits must be understood to be themaximum and minimum within which all of the compositions of ourinvention fall. Some of the vinylpyridine copolymers can be usedthroughout the given range, whereas some others, made from a differentvinylpyridine monomer or even from the same monomer but in a diiferentproportion of monomer to diolefin, can best be used over only a limitedportion of the given range. The exact optimum proportions can bedetermined in any specific case by simple preliminary experiment. Ingeneral, it can be said that the compositions of our invention have animpact strength of at least twice that of the vinyl chloride polymerfrom which they were made, and a flexural modulus of at least 100,000 p.s. i., as discussed in more detail hereinafter.

The compositions can be molded, calendered, extruded, or otherwisefabricated into articles of the desired shape, by the machinery andmethods conventionally used in making plastic articles. They are mostuseful in fabricating articles which need high impact strength incombination with rigidity, e. g., rigid sheets, rods, and many othermolded or extruded articles. The new compositions are especially usefulin making rigid pipe whichis much lighter in weight than metal pipe.

The compositions of the invention are prepared by intimately mixing thevinyl chloride polymer and the vinylpyridine elastomer together.Usually, the two materials are mixed together in the solid form by meansof a mixing machine of the type normally used for mixing rubber orplastics, e. g., a roll mill or a Banbury mixer. It is also possible tomix the two ingredients in dispersed form,

that is, the latices of the vinyl chloride polymer and the.

are. generallvadequate for:-this-:purpose.

3 themethod.ofmixingthetwo materials, itis necessary to heat the mixtureat somestage to a temperature above that at which the vinyl chloridepolymer fuses, in order to obtain an ladequately intimatecombination'of-thematerials. Temperatures within'thetrange of about2503.00 Without such heating the vinylichloride polymer will exist asdiscrete particles in the mixture, and the desired physical propertieswillnot be obtained. This heating is conveniently done either duringmixingon the mill or in the Banbury, or during thefinal molding. A ispref- .erably added to the mixture before heating, in order to minimizethe splitting off of hydrogen chloride, and to neutralizeany hydrogenchloride which does evolve. Hydrous tribasic lead sulfate, a typicalstabilizerfor polyvinyl chloride,- isan example of a suitablestabilizer.

The toughening effect of the vinylpyridine elastomer used in our ;vinylchloride polymer compositions differs radically from the softening orplasticizing efiect of conventional fplasticizers in that adequaterigidity of the compositions is retainedaud the impact strength isgreatly increased, whereas plasticizers markedly reduce the rigidity anddo not impart high impact strength. Thus, in a typical embodiment of theinvention, the impact strength can be raised from a value for the vinylchloride polymer itself of about 0.8 foot-pound per inch of-notch (lzod)to a value for the blend of from about 2 up to about 16 foot-poundswithout reducing the rigidity belowpractical limits.

it is.interesting to note that butadiene homopolymer does not raise theimpact strength of vinyl chloride polymers significantly. Consequently,it is most surprising to find that the diolefin-vinylpyridine copolymersimprove the impact strength to such an extraordinary extent. Thecopolymcr improves theimpact strength of polyvinyl chloride even thoughit is present in such a small amount as not to decrease the rigidity ofthe composition markedly.

The rigidity or flexibility is generally expressed in terms of theflexural modulus. Polyvinyl chloride itself has a flexural modulus at 25C. of about 400,000pounds per square inch. in general, it may be statedthat materials having a flexural modulus above 100,000 p. s. inaresufliciently stiff to be employed in'the usual applications requiring arigid material. However, it is preferred to use materials having afiexural modulus of at least 150,000 p. s. i. in fabricating rigidarticles. The preferred compositions of the invention are thereforethose having a flexural modulus of at least 150,000 p. s. i. The valuesrecorded in the examples herein are the actual measured valuesmultiplied by These compositions also have an impact strength of atleast twice that of the vinyl chloride polymer itself, and usually verymuch higher.

The polyvinyl chloride used in the invention is typified by thecommercially available resins known as the .Marvinols, e. g., MarvinolVR-lO and Marvinol'VR-ZO. iMarvinol VR-IO is used Where high heatstability is desired during processing, as in slush molding or in theextrusion of pipe. Its specific viscosity (0.4 g. of the Marvinol in 100cc. of nitrob'enzene) at 30 C. is 0.55. Marvinol VR- is a generalpurpose resin used in coated fabrics, unsupported film, electricalinsulation, etc. Its specific viscosity, measured in the same way, is0.38. Other polyvinyl chloride resins which are operable in ourinvention are exemplified by the commercially available materialsmarketed under such trade names as Geon 121, Geon 101, Geon 101-EP andVinylite QYNA. The vinyl chloride: vinyl acetate copolymers used areexemplified by commercially available resins known as Vinylites,especially those ranging in composition from about 85% to 96% of vinylchloride and correspondingly from about 15% to 4% of vinyl acetate.Certain of the Vinylites, e. g., VAGH and V MCH, which have a ratio ofvinyl chloride to vinyl acetate falling within these preferred limits,also contain, according to the manufacturer,'smallamounts of othermaterials. These Vinylites are operable in our invention, and-our use ofthe term vinyl chloridezvinyl acetate c9u b't .er und rst o o i clu theT vinyl chloridewinylidene chloride copolymers used contain from 1% upto 99% of vinylidene chloride. They are typified by the commercialmaterials sold under the trade name Saran.

The following examples illustrate our invention in more detail. Allcompositions are given in parts by weight. All of thevinylpyridinezdiolefin copolymers were made by emulsion copolymerizationin accordance with the conventional practice. The proportions of themonomers are given in form-of feed ratios.

Example 1 The following stocks were'made by stirring Marvinol powderwith 2-vinylpyridine:butadiene copolymer latices in the proportionsshown below, drying the mixtures, fusing them on a mill for 5 minutes at300-310" F., i. e., above the fusion temperature of the Marvinol, andmolding into fiat slabs at 338 F. for 10 minutes under pressure. StockA, which is shown forcontrast with the stocks B-G exemplifying ourinvention, was milled and molded in like manner.

Stock H A i B 1 C D i E F G Marvinol VR10 100 95 95 00 00 852-Vinylpyridine: butadieno col polymer lttex t 2 5 40:60... 5 10 15 60:4=10 i5 Izod impact strength (ft.-lbs./

111. of notch) 8 3.0 10 0 6.8 3.0 3.2 2.1 Flexural modulus at 25 C.

(thousands of p. s. i.) 440 368 375 311 259 324 260 "Polyvinyl chloride.Solid content.

Stock H was made by blending 5 parts of the coagulated2-vinylpyridine:butadiene copolymer.(40:60) with parts of Marvinol VR-lOon the mill at 300310 F., followed by molding as in Example 1. Theimpact strength was 12.7 and the flexural modulus 350,000, showing bycomparison with stock C that the materials canbe blended either in latexform or in solid form.

Similarly, the blending of Marvinol VR-lO with a comparable2-vinylpyridinezisoprene copolymer effects a considerable improvementinthe impact strength of the blends over'that of the Marvinol VR-10 alone.

Example 3 2-methyl-5-vinylpyridine and butadiene (40:60) werecopolymerized, and thelatex (containing 5 parts of solids) was blendedwith 95 parts of Marvinol VR10 powder. The mixture was treated as inExample 1. This stock (I) had animpact strength of 15.2 and a flexuralmodulus of 354,000. It is evident that this copolymer effects an evenmore remarkable improvement in the impact strength of the Marvinol thando the copolymers shown in Examples 1 and 2. l

The blends of the invention may be substituted to great advantageior theusual rubber or plastic compositions, or even for metals or othermaterials, in many applications where toughness is a requirem ent. Thus,the present mixtures may be used to fabricate parts for machines, suchas gears and cams; parts for textile machinery such as bobbins,shuttles, pickers, etc.; containers and pipes, especially for chemicaland the like operations where resistance to corrosive substances isdesired, as in filter press plates and tumbling barrels for platingoperations; electrical parts, such as terminal blocks, telephones, andprotective casings for cable joints as well as tote boxes and trays;luggage; radio cabinets; furniture; phonograph records; paneling orcovering for interior and exterior walls and surfaces of buildings,railroad cars or ships; automobile parts such as steering wheels, doorpanels, and seat parts; roller skate wheels; protective equipment suchas helmets, and armor, ineluding body armor; printing plates; tools; diecutting blocks; washing machine parts such as bearings and impellers;and numerous other articles, as will be evident to those skilled in theart. The blends may be laminated or otherwise reinforced, as with fibersor fabrics, if desired in making the foregoing or other articles,although usually the strength of the blends will be adequate withoutreinforcement.

Having thus described our invention, what we claim and desire to protectby Letters Patent is:

1. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 2 to 20 parts of a rubbery copolymer of from 40 to 80% of aconjugated diolefin with from 60 to 20% of a monoethylenicallyunsaturated monovinylpyridine, and (B) from 98 to 80 parts of a vinylchloride polymer.

2. A rigid thermoplastic composition characterized by high impartstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 3 to 15 parts of a rubbery copolymer of from 40 to 80% of aconjugated diolefin with from 60 to 20% of a monoethylenicallyunsaturated monovinylpyridine, and (B) from 97 to 85 parts of a vinylchloride polymer.

3. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 2 to 20 parts of a rubbery copolymer of from 40 to 80% of aconjugated diolefin with from 60 to 20% of a monoethylenicallyunsaturated monovinylpyridine, and (B) from 98 to 80 parts of polyvinylchloride.

4. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 3 to 15 parts of a rubbery copolymer of from 40 to 80% of aconjugated diolefin with from to 20% of a monoethylenically unsaturatedmonovinylpyridine, and (B) from 97 to 85 parts of polyvinyl chloride.

5. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 2 to 20 parts of a rubbery copolymer of from 40 to ofbutadiene with from 60 to 20% of 2-vinylpyridiue, and (B) from 98 to 80parts of polyvinyl chloride.

6. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 3 to 15 parts of a rubbery copolymer of from 40 to 80% ofbutadiene with from 60 to 20% of 2-vinylpyridine, and (B) from 97 toparts of polyvinyl chloride.

7. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 2 to 20 parts of a rubbery copolymer of from 40 to 80% ofbutadiene with from 60 to 20% of 2-methyl-5-vinylpyridine, and (B) from98 to 80 parts of polyvinyl chloride.

8. A rigid thermoplastic composition characterized by high impactstrength, comprising an unplasticized, intimate fusion-blended mixtureof (A) from 3 to 15 parts of a rubbery copolymer of from 40 to 80% ofbutadiene with from 60 to 20% of 2-methyl-5-vinylpyridine, and (B) from97 to 85 parts of polyvinyl chloride References Cited in the file ofthis patent UNITED STATES PATENTS 2,538,779 Harrison et al. Jan. 23,1951 2,614,089 Harrison et al. Oct. 14, 1952 2,614,093 Wheelock Oct. 14,1952 FOREIGN PATENTS 947,162 France Ian. 3, 1949

1. A RIGID THERMOPLASTIC COMPOSITION CHARACTERIZED BY HIGH IMPACTSTRENGTH, COMPRISING AN UNPLASTICIZED, INTIMATE FUSION-BLENDED MIXTUREOF (A) FROM 2 TO 20 PARTS OF A RUBBERY COPOLYMER OF FROM 40 TO 80% OF ACONJUGATED DIOLEFIN WITH FROM 60 TO 20% OF A MONOETHTYLENICALLYUNSATURATED MONOVINYLPYRIDINE, AND (B) FROM 98 TO 80 PARTS OF A VINYLCHLORIDE POLYMER.